The following United States patents comprise the closest known prior art:
U.S. Pat. Nos. 2,662,388; 2,723,874; 2,800,347; 3,425,247; 4,142,748; 4,143,529.
It is well known in the prior art to provide a door latch mechanism comprising a bolt extending therefrom to engage a strike and latch the door closed, the bolt being retractable to disengage the strike and permit opening of the door. Generally, such devices include a retractor which is driven by a cam rotatable by the spindle of a knob or handle assembly. The retractor acts against the resilient bias of a compression spring which maintains the bolt in the extended position.
Often it is desirable to provide such door latch mechanisms with a privacy lock to prevent opening of the door from one side thereof. This feature is attained by including a button or knob extending from one of the rosettes of the latch mechanism. The button or knob operates a shaft or the like which is actuable to lock the latch mechanism from the one side of the door which is provided with the button.
Due to the fact that doors may be hung in either left hand or right hand opening fashion, and that the privacy feature may be desirable on either side of such doors, it is necessary to manufacture prior art latch mechanisms with privacy locks so that they may be used in any combination of these parameters. As a result, it is necessary to manufacture and stock a large number of differing latch mechanisms and privacy lock mechanisms, causing higher costs to the manufacturers and consumers.